Display devices formed by two-dimensionally arranging pixels including an electrooptic element in the form of a matrix, for example liquid crystal display devices using a liquid crystal cell as an electrooptic element use an alternating-current driving method that reverses the polarity of a signal voltage applied to a pixel electrode with respect to the potential of a counter electrode of the liquid crystal cell in predetermined cycles. This is because degradation in resistivity of liquid crystal (resistance value specific to the material) or the like and an afterimage phenomenon referred to as “burn-in” occur when a direct-current voltage is applied to the liquid crystal cell over a long period of time.
Known as this alternating-current driving method are for example a 1H inversion driving method that inverts the polarity of a video signal Vsig in each H (H denotes a horizontal period) while a common voltage Vcom applied to the counter electrode of the liquid crystal cell is fixed, and a 1F inversion driving method that inverts the polarity of the video signal Vsig in each F (F refers to a field period, that is, a screen repetition period) while the common voltage Vcom applied to the counter electrode of the liquid crystal cell is fixed (see for example Japanese Patent Laid-open No. 2001-42287).
In a liquid crystal display device, a signal line for writing a video signal Vsig to pixels and a common line for supplying a common voltage Vcom common to each pixel to the counter electrode of a liquid crystal cell intersect each other, and there is a parasitic capacitance between the signal line and the common line. When the video signal Vsig is written to the signal line, coupling due to the parasitic capacitance causes the video signal Vsig to jump into the common line, and thereby the potential of the common line is swayed in a direction of the same polarity as that of the video signal Vsig, thus causing crosstalk.
For such a problem, the 1H inversion driving method inverts the potential of the signal line to which the video signal Vsig is written in each H, and can thereby cancel the swaying of the potential of the common line due to the coupling between lines (pixel rows), so that occurrence of the crosstalk caused by the coupling can be suppressed.
The 1F inversion driving method has advantages of being able to improve contrast and extend life using VA (Viewing Angle; vertical alignment) liquid crystal. On the other hand, the 1F inversion driving method writes a video signal Vsig of the same polarity to the signal line over a 1F period, and therefore cannot cancel the swaying of the potential of the common line due to the coupling between lines, so that occurrence of the crosstalk caused by the coupling cannot be suppressed.
When there is a large potential difference between pixel potential and signal line potential, a leak occurs in a switching element, for example a TFT (Thin Film Transistor) of a pixel due to difference in source/drain shape. The amount of the leak differs within one screen. Therefore, as shown in FIG. 11, shading, which causes degradation in picture quality, occurs. Specifically, taking as an example a case where the common voltage Vcom is 7.5 V and the signal line potential is 10.0 V on an H-side/5.0 V on an L-side (halftone), as shown in FIG. 12, for example, a screen upper part A, a screen central part B, and a screen lower part C have different leakage periods, and thereby an amount of leakage differs within one screen. Thus, there is little effect of leakage in the screen upper part A, the screen central part B becomes somewhat whitish due to an effect of leakage, and the screen lower part C becomes whitish due to an effect of leakage, so that shading occurs.